/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.iotdb.db.metadata.tag;

import org.apache.commons.io.FileUtils;
import org.apache.iotdb.commons.exception.MetadataException;
import org.apache.iotdb.commons.file.SystemFileFactory;
import org.apache.iotdb.db.conf.IoTDBDescriptor;
import org.apache.iotdb.tsfile.utils.Pair;
import org.apache.iotdb.tsfile.utils.ReadWriteIOUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.File;
import java.io.IOException;
import java.nio.BufferOverflowException;
import java.nio.ByteBuffer;
import java.nio.channels.ClosedByInterruptException;
import java.nio.channels.FileChannel;
import java.nio.file.StandardOpenOption;
import java.util.Collections;
import java.util.Map;

public class TagLogFile implements AutoCloseable {

    private static final Logger logger = LoggerFactory.getLogger(TagLogFile.class);
    private File tagFile;
    private FileChannel fileChannel;
    private static final String LENGTH_EXCEED_MSG =
            "Tag/Attribute exceeds the max length limit. "
                    + "Please enlarge tag_attribute_total_size in iotdb-common.properties";

    private static final int MAX_LENGTH =
            IoTDBDescriptor.getInstance().getConfig().getTagAttributeTotalSize();

    private static final int RECORD_FLUSH_INTERVAL =
            IoTDBDescriptor.getInstance().getConfig().getTagAttributeFlushInterval();
    private int unFlushedRecordNum = 0;

    public TagLogFile(String schemaDir, String logFileName) throws IOException {

        File metadataDir = SystemFileFactory.INSTANCE.getFile(schemaDir);
        if (!metadataDir.exists()) {
            if (metadataDir.mkdirs()) {
                logger.info("create schema folder {}.", metadataDir);
            } else {
                logger.info("create schema folder {} failed.", metadataDir);
            }
        }

        tagFile = SystemFileFactory.INSTANCE.getFile(schemaDir + File.separator + logFileName);

        this.fileChannel =
                FileChannel.open(
                        tagFile.toPath(),
                        StandardOpenOption.READ,
                        StandardOpenOption.WRITE,
                        StandardOpenOption.CREATE);
        // move the current position to the tail of the file
        try {
            this.fileChannel.position(fileChannel.size());
        } catch (ClosedByInterruptException e) {
            // ignore
        }
    }

    public synchronized void copyTo(File targetFile) throws IOException {
        // flush os buffer
        fileChannel.force(true);
        FileUtils.copyFile(tagFile, targetFile);
    }

    /**
     * @return tags map, attributes map
     */
    public Pair<Map<String, String>, Map<String, String>> read(int size, long position)
            throws IOException {
        if (position < 0) {
            return new Pair<>(Collections.emptyMap(), Collections.emptyMap());
        }
        ByteBuffer byteBuffer = ByteBuffer.allocate(size);
        fileChannel.read(byteBuffer, position);
        byteBuffer.flip();
        return new Pair<>(ReadWriteIOUtils.readMap(byteBuffer), ReadWriteIOUtils.readMap(byteBuffer));
    }

    public Map<String, String> readTag(int size, long position) throws IOException {
        ByteBuffer byteBuffer = ByteBuffer.allocate(size);
        fileChannel.read(byteBuffer, position);
        byteBuffer.flip();
        return ReadWriteIOUtils.readMap(byteBuffer);
    }

    public long write(Map<String, String> tagMap, Map<String, String> attributeMap)
            throws IOException, MetadataException {
        ByteBuffer byteBuffer = convertMapToByteBuffer(tagMap, attributeMap);
        return write(byteBuffer, -1);
    }

    /**
     * This method does not modify this file's current position.
     */
    public void write(Map<String, String> tagMap, Map<String, String> attributeMap, long position)
            throws IOException, MetadataException {
        ByteBuffer byteBuffer = convertMapToByteBuffer(tagMap, attributeMap);
        write(byteBuffer, position);
    }

    /**
     * @param byteBuffer the data of record to be persisted
     * @param position   the target position to store the record in tagFile
     * @return beginning position of the record in tagFile
     */
    private synchronized long write(ByteBuffer byteBuffer, long position) throws IOException {
        if (position < 0) {
            // append the record to file tail
            position = fileChannel.size();
        }
        fileChannel.write(byteBuffer, position);
        unFlushedRecordNum++;
        if (unFlushedRecordNum >= RECORD_FLUSH_INTERVAL) {
            fileChannel.force(true);
            unFlushedRecordNum = 0;
        }
        return position;
    }

    private ByteBuffer convertMapToByteBuffer(
            Map<String, String> tagMap, Map<String, String> attributeMap) throws MetadataException {
        ByteBuffer byteBuffer = ByteBuffer.allocate(MAX_LENGTH);
        serializeMap(tagMap, byteBuffer);
        serializeMap(attributeMap, byteBuffer);

        // set position to 0 and the content in this buffer could be read
        byteBuffer.position(0);
        return byteBuffer;
    }

    private void serializeMap(Map<String, String> map, ByteBuffer byteBuffer)
            throws MetadataException {
        try {
            if (map == null) {
                ReadWriteIOUtils.write(0, byteBuffer);
            } else {
                ReadWriteIOUtils.write(map, byteBuffer);
            }
        } catch (BufferOverflowException e) {
            throw new MetadataException(LENGTH_EXCEED_MSG);
        }
    }

    @Override
    public void close() throws IOException {
        fileChannel.force(true);
        fileChannel.close();
        fileChannel = null;
    }
}
